Patent GB-473691-A (GB)
Title: Improvements in and relating to grinding or abrading machines
IPC: B24B49/04
Filed: 1936-03-11
Abstract: 473,691. Grinding. TRIGGS, W. W. (Norton Co.) March 11, 1936, No. 7389. [Class 60] A cylindrical-grinding machine, in which the wheel is fed towards and from the work by fluid-pressure-operated means, has valve mechanism whereby the wheel is fed rapidly to operative position, and then slowly to grind the work a calipering device including electric circuits operating, when the work has reached a predetermined size, to actuate the valve mechanism to stop the feed, and, when the work has reached the finished size to cause withdrawal of the wheel from the work. The machine comprises a bed 10 upon which is movable, on ways 16, 17, a grinding-wheel slide 11 carrying a wheel 12, to operate on a piece of work 22 rotatably carried on a table 18, which may be traversed on ways 19, 20. The slide 11 is movable by a screw 33 operable through gearing from a shaft 40 rotatable manually, or by movement of a clutch 57, by a pinion 50 and a rack 48 carried by the rod 47 of a piston 46 movable in a cylinder 45, to which fluid is supplied from a tank 92 by a pump 89, the fluid passing along a pipe 93 to a reversing valve 95. The valve 95 has two pistons 100, 101 and controls flow to and from ports 104, 105 and exhaust ports 112, 114, the port 112 communicating directly with the tank and operating during rearward movement of the slide 11, and the port 114 communicating with a port 120 in a feed control valve 121, which controls the rate of feed by throttling the exhaust through an elongated port 127, which is covered to a degree depending upon the position of a spring-pressed piston 123 carried by a rod 124 and movable in a casing 126. The control valve is operated by means of a collar 135 on the piston rod 47, the collar engaging an arm 140 of a member 137 slidable on a fixed guide rod 138 and also having an arm 141 adjustably clamped to the rod 124, so that as the piston 46 moves to the right, to move the wheel 12 away from the work, the piston 123 is moved to the right completely to uncover the port 127, whereas, when the piston 46 moves to the left to feed the wheel up to the work, the piston 123 moves to the left under control of a bell-crank lever 144 journalled on the rod 138. The lever 144 has an arm 148 carrying a head 149 which carries a stud 150 and an adjustable set screw 152, and, when the lever is positioned normally under gravity, the stud 150 is engaged by the end of rod 124, thus preventing covering of the port 127. The wheel slide thus moves rapidly up to grinding position, when the collar 135 engages a cam surface 157 on the arm 155 of the lever 144, moving the stud out of, and the screw 150 into alignment with the rod 124, so that the piston may partially close the port 127 and slow down the wheel feed ; when the work has reached a predetermined size the screw 152 is lifted by electrical means, permitting piston 123 to close the port 127 and stop the feed. The work is gauged by a calipering device comprising a head 160, within which is a sleeve 165 carrying a slidable feeler rod 162 carrying a hard work-engaging point, the sleeve also carrying screws 168, 166 to engage the work to locate the feeler thereon. The rod 162 is engaged by a micrometer screw 170 in a lever formed of parts 174, 175, 176 and supported by knife edges in grooves in studs in the casing, springs 200, 203 also engaging the lever. The lever carries an electrical contact to engage an adjustable contact spring 210, and a depending arm 182 of the lever carries a contact 222 to engage a contact spring 211 ; the contact 219 is broken and feed is stopped when the work nearly reaches the desired diameter, and the contact 222 is broken when the exact diameter is reached, the final grinding being given without positive feed of the wheel 12. The calipering device is mounted on a bracket 231 on the wheel guard by means of a post 233, adjustable member 234, pivoted member 236, and an adjustable rod 244, the rod carrying a bracket 242 to which is pivoted a link 247 pivotally carrying the casing 160, a spring device 256 serving to swing the link 247 to overcome the weight of the device when in use. When not in use the whole device is swung about the pivot 237 of member 236, and in order to maintain the circuit, of contact 219, a switch 230 is provided. A switch 272, 273 operated by a button and in parallel with switch 230 also is provided in casing 160 and is held closed by the operator as the casing is lowered on to the work ; this maintains the circuit closed after switch 230 opens. In order to avoid arcing, a low tension circuit from battery 276 is employed in the caliper circuits, which control relays 284, 286, the arms 308, 326 of which, when the relay circuits are interrupted, close a high tension supply from lines 304, 310 to operate solenoids 294, 315, the solenoid 294, when the contact 219 is opened by movement of the feeler rod when the work is to a desired size, lifting the head 149 so that both the stud 150 and screw 152 clear the piston rod 124, thus allowing the piston 123 to close the port 127 and stop the feed of the wheel 12. When the contact 222, is opened upon the work reaching finished size, de-energizing the relay 286, the circuit of solenoid 315 is closed moving the armature 318 connected to the reversing valve rod 102 to cause reversal of the movement of the wheel slide 11. The reversing valve is moved to forward feeding position by a lever 103 which moves an arm 333, the head 334 of which engages the armature 318 ; the lever is normally held vertical by a spring plunger 335, and moving the lever to operative position also closes two switches 341, 342 to energize the relays 284, 286 and so de-energize the solenoids until the caliper is again in contact with the work, and a further switch 375 operated by the lever 144 in series with switch 342 also is provided to hold the relay-circuit 286 closed, the switch 375 being opened when the lever is rocked to bring the screw 152 into operative position. In operation, the work is placed in the machine, and the lever 103 is moved to position 103a starting the feed of the wheel, which proceeds rapidly until the collar 135 operates the control valve, the feed then proceeding slowly until the caliper feeler descends sufficiently to open the contact 219, when the solenoid 294 is energized to stop the feed. Grinding then proceeds by spring of the machine parts until contact 222 opens, when solenoid 315 is energized to operate the reversing valve and withdraw the wheel from the work.